The invention relates to an arrangement for the exclusive connection of a selectable specimen from a plurality of loads, each of which can be switched on via an individual activation switch between the poles of a voltage source.
Arrangements of this type are required if there is a need to prevent various electrical loads being set in operation at the same time, whether it is unintentional or deliberate. In many cases, switching on of more than one load simultaneously can lead to undesirable results, for instance when, a common current supply source is overloaded, or if loads which are switched on simultaneously interfere with one another in their operation or effect. Devices for example, which serve for the spatial adjustment of objects of various sizes, frequently contain a corresponding plurality of electrical drives, the simultaneous activation of which could not be dealt with by the adjustment mechanism or which would make control more difficult for the user or which would overload the current supply source beyond the desired amount. This can arise in motor vehicles, for instance in the devices for adjusting the seat or the steering column.
Various devices are known for the mutual interlocking of any number of switch devices such that only one of the switch devices can be switched on, see for instance, known devices described in DE-PS 1 040 111, DE-AS 20 08 460 and 20 57 296 and also DE 30 26 619 C2. In the devices described there, the switch devices are respectively electromechanical relays, each of which contain further contacts besides the main contact forming the actual circuit break, for instance for the lock of the relay and/or for closing and opening of additional auxiliary circuit breaks which interrupt, upon actuation of the relay, the exciting currents of the respective other relays.
In a known device described in DE-AS 1 640 995, the simultaneous activation of several relays is prevented by a resistor which is switched on before a common exciting current-supply transmission line to the relays. A large drop in voltage occurs across the resistor, upon simultaneous actuation of two or more switches, such that the residual voltage remaining between the transmission lines no longer suffices to allow a relay coil to respond. This embodiment may function without additional relay contacts, but it is sensitive to fluctuations in the supply voltage and requires very exact designing of the electrical components.
A further disadvantage in the above-mentioned known arrangements is that actuation of the switch devices is only possible via contact switches.